ABSTRACT
Mechanized tunnelling is the most used construction method for long tunnels because of its high excavation rate and enhanced worker safety. The study of the interaction between the ground, the Tunnel Boring Machine (TBM) and the supports is paramount for the structural design of the segmental lining and to assess the risk of entrapment of a TBM. Despite the three-dimensional nature of the problem, 3D numerical calculations are rarely employed in the design practice because are time-consuming and demand advanced numerical skills. The use of full axial-symmetric analyses significantly reduces the elapsing time and allows for sensitivity studies. However, the simulation of the problem is still complex, and some authors proposed different numerical strategies for Shielded TBM. The proper simulation of the ground closure on the TBM shield requires the use of large strain formulations or alternatively the application of special boundary conditions at the tunnel wall when small strain formulations are adopted. The results of numerical analyses, performed using large strain formulations in full axial-symmetric conditions, are presented in this paper. The numerical outcomes have been compared with reliable data obtained using small strain formulations presented in the literature. This study shows the possibility of using large strain formulations to simulate the ground-shield-lining interaction but also highlights limitations and disadvantages of this approach.
